CFM needed to keep a 400w cool?

how much cfm would my fan have to pull through the reflector with a 400 hps to keep a 2ft x 5ft x7ft closet cool?

Currently I have a 250 cfm in a 2x6x8 room. It keeps it cool but I don't think it's enough. The temp stays at 81.5 F. I also have a fan that points straight at the bulb's glass shield.

NEW High Pressure Sodium 400 watt HPS Grow Light w 400w - eBay (item 160211130805 end time Mar-11-08 17:00:00 PDT)

k well i was thinkin about getting this, and their upgrades to have it aircooled are to expensive so i thought id just make my own setup, home depot has 250 cfm inline duct fans for like 30 bucks

You will still need an exhaust in the top of the room to get rid of heat. I have a cooltube and even with it, i still have to use the exhaust to get rid of the heat in the room. Cooltubes are nice but they are not the answer to removing all the heat in a room.

Hoss,

Proper Airflow is important. I'm experiencing a heat issue right now.

First, I'd recommend you get a "Cool Tube" fixture. I've got one and it works great.

My area is 2x6x8'. My problem is the tops roast in high temps while the bottom turns to schwag because of low temps and less Lumen Love. After a week or two I've got it stabilized, 88F top and 71F ground. It was around 100F up top and 67F at ground. I added a bunch of fans.

So even though I can direct the heat, make-up air is is sucking in the exhaust.... I need to vent through a wall.

I'm in an apartment. I can't punch any exhaust holes into the walls. So I sorta vent with Flex connected to the cool tube connected to a fan that gets recirculated right back into the light.

Think of a way you can exhaust through a wall opposite the area opening or to the ceiling.

You can get away with less CFM's if you engineer your air system a little bit.

Good Luck.

"recirculated right back into the light"

To clarify, I don't have a closed system. I can't duct the heat away far enough from the source. So it gets sucked in the supply side and recirculates.

This is a sealed metal unit with a thick piece of saftey glass to seal it. You need a 6" squirrel fan that draws in cool, outside air, through the fixture. If you can manage to route the 6" tubing (through flanged holes in the walls or ceiling) you will have NO heat problems in the grow area at all. The trick is being able to cut dem holes.

I am using a 400 watt in a 2 x 4 x 7 closet and using a 50 cfm bathroom fan from home depot for 12.00 i believe, And I did this without cutting anyholes in the apartment. It's not as loud as they claim, I have an air filter sitting on top and with it on you can't hair the exhaust fan at all. I exhaust the air out side the window. The window is on the second floor and is cracked open 1 inch which is completely unnoticeable from the ground. A square cardboard tube connects the 3 inch vent tube to the window crack and is completely sealed across the length of the window. With the blinds sitting directly on top of the cardboard tube I taped cardboard over the entire window to block light. The entire exhaust is hidden behind the curtains and completely hidden Hope this helps give you some ideas Be creative.

rmax said:

"recirculated right back into the light"

To clarify, I don't have a closed system. I can't duct the heat away far enough from the source. So it gets sucked in the supply side and recirculates.

Click to expand...

Isn't that a textbook description of a closed loop system?

Big,

Wise Guy??

I would say a "Closed-Loop" is the air circulating continuously inside the flex, light and fan while never exchanging with fresh air.

An Automobile Radiator Cooling system would be a "Closed-Loop" example.

???

rmax said:

Big,

Wise Guy??

I would say a "Closed-Loop" is the air circulating continuously inside the flex, light and fan while never exchanging with fresh air.

An Automobile Radiator Cooling system would be a "Closed-Loop" example.

???

Click to expand...

Me? A wise guy? surely you jest!

Just busting chops. But your description wasn't that clear to me. (yup, short bus guy here )

So is the air coming out of the flex going back into the same room?

(now an indirect system can work as closed. Take the flex, run it, say outside, or have the AC blowing on the flex to cool it, and then back to the lamp on the other side. But you are going to need a lot of surface area to make that work well; not practical.)

"So is the air coming out of the flex going back into the same room?"

For me it is. I'm using a closet. So when I vent from the closet door, the hot air is blown right in front of the setup. Then, heat rises and is sucked back through the system. It's a mess.

If you can, blow the air though a wall or the ceiling.

i think im gunna vent through the wall so its blowing into my room, double as extra heating

i bet you could macgyver up a water cool system for pretty cheap under 25 bucks

Johnnysiqq said:

i bet you could macgyver up a water cool system for pretty cheap under 25 bucks

Click to expand...

I was pondering that. I have a nice radiator (from a 3000W HV cab to a CNC laser and a pump I used to use for a PC cooling set up.)

But there are issues. How are you going to cool the air? The water has to be quite a bit cooler then the air (by about 30F) Surface area is the key here. A turbo charger's intercooler might work, but thats an air to air heat exchanger.

A typical radiator (car style, many tubes with fins) is a air:water, but how are you going to cool the water? The air will eventually heat up the water passing through the radiator. A second radiator with a fan? (probably need 2 to cool the water for each one to cool the air.)

Swamp cooler? i posted abut that. but its gonna increase the humidity. Unless you do indirect. Thats a bit complicated, not much diff from the radiator.

Hey. I'm up for ideas. I think there is a simple solution out there somewhere. Got one?.
(cross the plant with a mushroom, so it grows in the dark )

you could take a 5 gal bucket and put a pump in it and tube to a home made heat exchanger as long as the bucket isnt in the grow room the bucket should cool off the water before it renters the system the water will go back to room temp. or if its still too hot then put another heat exchanger before the hot water goes back into the 5 gal

I kinda said that. Plus that extra heat exchanger needs air cooler then the water, flowing at a good clip across that extra heat exchanger. Air doesn't change water temp that fast.

We are approaching it being cheaper, easier, and more effective to add an AC to the grow room. (if basic ventilation isn't enough)


Geo-therm might be a way to go. A reservoir down just below the frost line should help keep the water at a even temp. Just need a pump with a good head. (and a few mexicans to do the diggin)

ac units still need to vent to the outside and they use alot of power like 500 watts or more and your gonna be shellin out 300 bucks for one. i think opening up the system is a lot simple and cheaper way out of this one